Method of creping tissue and product thereof



Aug. 15, 1961 E. H. VOIGTMAN ET Al. 2,996,424

METHOD OF CREPING TISSUE AND PRODUCT THEREOF Original Filed Feb. 12,1957 2 Sheets-Sheet l Aug- 1961 E. H. VOIGTMAN ET AL 2,996,424

METHOD OF CREPING TISSUE AND PRODUCT THEREOF 2 Sheets-Sheet 2 OriginalFiled Feb. 12, 195'? Divided and this application Mar. 20, 1959, Ser.No. 800,821

4 Claims. (Cl. 162-112) This invention in general relates to an improvedtissue structure and a method of making the same. This invention moreparticularly relates to improved multi-ply creped cellulosic tissueproducts and the manufacture thereof.

This application is a division of application Serial No. 639,792, filedFebruary 12, 1957.

Multi-ply creped tissue products utilized for certain applications suchas for packaging, padding, cushioning, insulating, wiping, etc. requirelow density and high bulk. Where prior multi-ply creped tissue products,such as are used for insulating and cushioning, were manufactured so asto exhibit especially low density and high bulk, it was found they couldbe easily and permanently compressed or crushed to a condition of higherdensity and lower bulk. Accordingly, the originally high insulating andcushioning properties of these tissue products were materially reducedwhen subjected to stress.

Ditficulties have also been encountered in providing multi-ply tissueproducts for wiping purposes which not only are of low density and highbulk and are relatively self-supporting and stable during use, but whichalso have a greatly decreased tendency to lint or cast off free fibers,and have a sufficiently coarse surface or bite to easily remove from thesurface to be cleaned dirt, grime and other discrete substances.

It has now been found that improved multi-ply cellulosic tissue productscan be fabricated by diiierentially creping cellulosic tissue sheets ina suitable manner and then combining them to provide in the productsimproved structural stability, together with high bulk and low density.These high bulk and low density characteristics are retained even whensuch products are subjected to considerable compressive force.Accordingly, the improved multi-ply products are highly satisfactory foruse as packing and padding materials.

The multi-ply cellulosic tissue products of the present inventionpresent relatively coarse, uneven surfaces, so that they are alsoadaptable as wiping agents. Furthermore, the fibers of these productsare more strongly bonded to each other in selected areas and have lesstendency to lint, which adds to their utility as wiping agents.

The improved cellulosic tissue products of the present invention whichcomprise a plurality of plies of differentially creped cellulosic tissueare fabricated in a wholly unique manner in accordance with the methodof the present invention.

Accordingly, it is an object of this invention to provide improved,stable, creped, cellulosic tissue products and a method of making thesame. More specifically, it is also an object of this invention toprovide novel creped tissue products which, as a result of adifferential creping process, are relatively lint free and have improvedcoarse surfaces with improved bite characteristics, and a method ofmaking the same. It is a further object of this invention to providemeans and procedures for obtaining stable, differentially creped,multi-ply, cellulosic tissue products having improved low density andhigh bulk characteristics.

Further objects of this invention all be apparent from V the followingdetailed description and the accompanying drawings of which:

FIGURE 1 is an isometric View and partial cross section of a multi-plytissue product of the present invention;

FIGURE 2 is a schematic representation of apparatus on which thedifferential creping of the present invention may be carried out; and

FIGURE 3 is a somewhat schematic representation of a micro-jet sprayboom in relation to the drier surface.

Referring now more particularly to the accompanying drawings, FIGURE 1shows a multi-ply, differentially creped tissue product, produced inaccordance with the present invention. The illustrated product comprisesa plurality of superposed, cellulosic tissue webs or sheets 5. For thepurposes of the present invention, the number of plies utilized in theproduct may be two or more, depending upon the particular applicationfor which the product is to be used. The individual sheets in theproduct are formed tissue webs having a basis weight, on a bone drybasis, before differential creping of between about 3.5 pounds and about15 pounds per ream of 3,000 square feet. The preferred basis weightrange for these sheets depends upon the particular end use for which theproducts are intended. For example, if the sheets are to be utilized forcushioning or insulating purposes, the preferred basis weight range isbetween about 4.5 pounds and about 7.5 pounds per ream of 3,000 squarefeet, on a bone dry basis, before dilferential creping. For wipingpurposes, this preferred range is 9 to 15 pounds per ream.

Each of the cellulosic tissue webs or sheets 5 has a series ofalternating coarsely creped areas 7 and more finely creped areas 9. Thealternating coarsely creped areas 7 and more finely creped areas 9provide alternating puffed and flat areas which give the product itsunique properties. The fine crepes in the flat areas function asstabilizers holding the arches of the coarse crepe in place and enablingthe latter to act as structural members to provide the product with itsstable bulk characteristics. Although in FIGURE 1 these areas are shownas being a series of rather broad parallel bands, they may be in anysuitable pattern such as diagonals, concentric circles, dots, squares,discontinuous areas, cross-hatched areas and the like. It is important,however, that the coarsely creped and more finely creped areas alternateor are interspersed so as to provide structural stability to each of thecoarsely creped areas of the web. When alternated properly the finelycreped areas act in the manner of a structural truss to hold thecoarsely creped areas in position.

It is well known in the art that up to a certain degree, coarser crepingcan be achieved by using thicker creping blades. However, this does notprovide a product having the stabilized increased bulk of the presentinvention since the coarser crepe so produced has an incipient tendencyto collapse or flatten out, and therefore has very little ability tosupport loads under stress. In the present invention, the coarselycreped areas provide vertical components of large comparative magnitude,while the finer creping imparts a structural rigidity to the coarsecrepe to provide a relatively stable product of increased bulk and lowdensity.

The coarsely creped areas 7 of the plies of the tissue product shouldhave been about 5 and about 30 crepes per inch as the product is woundonto the reel at the end of the paper machine, and preferably betweenabout 10 and 20 crepes per inch. The more finely creped areas 9 of therespective plies should have between about 20 and about 200 crepes perinch, and preferably between about 30 and about 50 crepes per inch, Somestretching usually takes place as the sheets are plied up into theproduct of this invention, to the extent of about percent of theirlength.

The webs or sheets comprising the plies of the product have a creperatio between about 1.25 and 2.5. A crepe ratio of about 2.0 ispreferred. By crepe ratio is meant the ratio of the length of the flatsheet before creping to the length of the sheet after creping.

The coarsely creped areas 7 of the plies of the product should comprisebetween about percent and about 85 percent of the total area of each ofthe plies, preferably between about percent and about 60 percent. Thefinely creped areas 9 of the plies comprise the remainder of the crepedarea of the plies. The respective plies of the product may be assembledin uniform or in random distribution with respect to the alignment orcoarsely creped and finely creped areas of the plies. After the tissuesheets are assembled the multi-ply product of the present invention hasa density between about 1.3 pounds and about 2.0 pounds per cubic foot.The product has a bulk up to about 100 percent greater than comparableconventionally creped tissue products.

The manufacture of improved multi-ply creped cellulosic tissue productsin accordance with the present invention involves the steps of formingsheets or webs of tissue in a conventional manner and thendifferentially creping each of the tissue webs or sheets so as toprovide alternating or discontinuous: desired areas of coarse crepe andof more fine crepe. A plurality of the individual sheets o'r Webs of thedifferentially creped tissue are then assembled into a unitary structurewhich is the improved multi-ply tissue product of the present invention,as illustrated in FIGURE 1.

In accordance with the method of the present invention, a sheet or webof fibrous tissue is formed by a water-laying technique on the usualFourdrinier-type web forming equipment. The mat of fibers of which theweb is composed is formed by applying to the upper surface of the'Fourdrinier wire, as by flowing thereon, a layer of stock containingthe required amount of fibers in an amount of water which is suflicientto produce the proper distribution of the fibers in the web, andsubsequently eliminating sufiicient of the water to produce a coherentweb or sheet capable of being couched off the end of the For thepurposes of the present invention, the sheet may be made of variouscellulosic and other fibers which are normally used in the fabricationof tissue webs or sheets. The proportions and types of such fibers maybe adjusted in accordance with the uses to which the tissue product isto be applied. The useful cellulosic fibers include chemical wood pulpfibers, mechanically produced wood pulp fibers, cotton fibers, etc.Suitable chemical wood pulp fibers include those produced by thesulfite, sulfate and semi-chemical pulping processes. The fibers may bebleached, but this is purely a matter of choice, depending upon the typeof end product desired. Various synthetic fibers such as rayon, nylon,glass, polyvinyl chloride and cellulose acetate fibers may be added invarying amounts to the furnish to provide webs having certain specificproperties. The furnish is mixed with a suitable amount of water to makeup a stock or suspension.

The tissue web may be formed on a Fourdrinier webforming machine havingan open or spout type head box or on a cylinder vat machine. The driersection of a Fourdrinier machine is illustrated generally in the schematic view, \FIGURE 2.

As produced on such a machine the formed cellulosic tissue web normallyhas a moisture content of approximately 85 percent by weight as itleaves the wire before drying. Moisture content of the web is furtherreduced to between 70 and 80 percent by the main press and to about 65percent as the web is applied to the drier by the press roll. The dryingof the tissue web comprises re- 4 ducing the moisture content thereof byheat to between about 3 percent and about 14 percent by weight of thetissue, on a bone dry basis. The drying operation is carried out in theconventional manner on a single, large diameter, heated drier roll ofthe Yankee type. The Yankee drier comprises a heated cylinder which maybe as large as 15 feet or more in diameter and of equal or greaterlength. It may be fabricated from a single casting of cast iron which isground to a smooth surface. Alternatively, the Yankee drier may beconstructed as set forth in Us. Patent No. 2,725,640 of December 6,1955, to Voigtman, or may be of any other suitable design or material.

Referring now more particularly to FIGURE 2 of the accompanyingdrawings, the wet tissue web 11 after being couched in the usual mannerfrom the forming wire 10 at a moisture content of about 85 percent, iscarried by a top felt 13 through the main press which includes a toppress roll 15, a bottom suction press roll 17 and a bottom felt 18. Thepress ro'lls partially dewater the wet web to a moisture content ofabout 70 percent to about 75 percent by weight, on a bone dry basis. Theweb 11 is then carried by the top felt 13 around the usual tail roll 19,and into the pressure nip between the Yankee drier cylinder 21 and arubber covered suction press roll 23. Press roll 23 acts to press web11. firmly o'nto the sur face of cylinder 21. At this point the moisturecontent of the web is about 65 percent by weight.

As indicated in FIGURE 2, cylinder 21 rotates in a clockwise direction,carrying web 11 with it during rotation. The creped web is wound up intoa soft roll or reel 25 which rotates at a controlled peripheral speed.The drier operates at an even surface temperature between about F. andabout 212 F. and normally rotates at surface speeds in excess of 1,000feet per minute. At this temperature and speed of rotation the Web isreduced to a moisture content of between about 3 and 14 percent byweight before it is creped. Beyond the pressure nip, top felt 13 leavesweb 11, and passes around roll 27 and associated rolls to return forreuse in the processing of the tissue web.

Referring again to FIGURE 2, as cylinder 21 rotates, means 29continuously applies a release agent in a predetermined pattern to theadjacent surface of cylinder 21.

The release agent for the puiposes of the present invention may be oneor more compounds which are miscible with water or another volatilecarrier. By miscible is meant dispersible in or soluble in the volatilecarrier. Air also can be used as the carnier, applying the release agentin the form of a mist. The release agent must impart a degree ofoiliness to steel of less than 0.3 at 20 C., expressed as thecoefiicient of friction, determined as described later in thisspecification.

. In FIGURE 3, means 29 is shown as a boom 31 having spaced micro-jets33 directed at the adjacent drier surface 35 and extending substantiallyover the entire width of the drier 21. The release agent is appliedtothe drier surface in a predetermined pattern for differential creping,as hereinafter more specifically set forth. Generally, enough releaseagent must be applied to form a film on predetermined areas only of thedrier surface. This film should be substantially completely absorbed bythe web on the drier, so that there is substantially no residual releaseagent left on the drier surface beyond the creping doctor blade. Theoptimum amount of release agent suitable for the purposes of the presentinvention is just short of that which would leave a residual amount onthe drier. However, a small residual is not detrimental to the processprovided it does not cause excessive build up on the surface of thedrier. These release agents have been used with varying degrees ofeffectiveness in amounts ranging from 0.5 pound to 50 pounds per ton ofproduct. (The preferred operating range is from 1 to 10 pounds per ton.)

Any other apparatus which applies the release agent to the drier surfacein a controlled pattern may be utilized in this invention. In thisconnection, a patterned rubber printing roll may be used. If such aprinting roll is keyed to the drier so that it prints the pattern inexam register at each revolution, the exact control of the amount ofrelease agent used is not as critical because a residual carryover doesnot alter the pattern. In addition, an arrangement of wicks or otherequipment to wipe the release agent on certain areas of the driersurface may be used.

The release agent should be applied in a pattern to the exposed Yankeedrier surface between the conventional creping doctor blade 37, attachedto the drier, and the nip between drier cylinder 21 and press roll 23,as shown in FIGURE 2. Moreover, the point of application of the releaseagent should be so chosen as to allow a sufficient period of time toelapse before the release agent on the drier surface enters thepreviously-mentioned nip. This is to allow the volatile components ofthe release agent on the drier surface to evaporate and leave behind thegreasy or oily residue in a non-migrating pattern on the drier surface,which pattern will not substantially spread in the nip between the pressroll and drier. Accordingly, it is preferred to apply the release agentrelatively near the creping doctor blade. The optimal point ofapplication of the release agent necessarily depends on the amount andconcentration of release agent applied to the drier surface, the surfacetemperature of the drier and the nature of the volatile constituents ofthe release agent.

In the event a series of heated drier rolls are utilized in place of theYankee drier, the release agent is applied in the previously describedmanner to the exposed surface of the drier roll on which the creping isperformed and prior to the pressure nip between the drier roll andassociated press roll.

It is also within the scope of the present invention to apply therelease agent in a pattern to the exposed surface of the web, as by apatterned rubber printing roll, while the web is on the Yankee or otherdrier roll, so as to allow the pattern of release agent to penetrate theweb to the drier surface and thereby effect the desired differentialrelease of the web. In this connection, the point of application of thepattern of release agent to the web on the drier should be chosen so asto allow sufficient penetration of the release agent and evaporation ofits volatile constituents, thereby assuring substantial dilferentialrelease of the web.

As web 11 is carried on cylinder 21, as shown in FIGURE 2, it dried to amoisture content of between about 3 and about 14 percent by weight bythe time it reaches the creping doctor blade 37. This blade dry crepesthe web from the drier.

It should be noted that the web is dry creped, as distinguished from wetcreped or semi-creped, that is, the web is dried shortly after forming,and is creped directly oflf the drier at a moisture content usually lessthan 14 percent. In wet creping, the sheet is dried, then rewetted andreapplied to a drier and creped therefrom. In semicreping, the doctorblade is used on a drier usually located about half way along in thedrier section and produces only a limited amount of crepe (in thevicinity of 5 to 15 percent). The natural adherence of the tissue web tothe surface of the drying cylinder is reduced in those places where therelease agent is present. Consequently, as the web is creped from thedrier surface by the scrap ing action of the creping doctor blade, itassumes a differential crepe pattern caused by this differential degreeof adherence to the drier surface.

It is important to recognize that the present invention is directedprimarily to the dry creping process. The products produced by drycreping differ materially from those produced by wet creping andsemi-creping, both in their appearance and in their functionalcharacteristics.

The release agent is applied to the drier surface to control thephysical characteristics of the creping. The

new

more easily the dried web is released from the drier sufface, thecoarser the type of creping effected by the creping doctor blade.Accordingly, when the release agent is applied to the surface of thedrier in a pattern, there Wiil be a corresponding pattern of coarsecrepe in the creped web. In the surface areas of the drier leftuntreated with release agent the corresponding areas of the web will bereleased in the normal manner. Consequently, these areas will be morefinely creped.

The differentially dry creped tissue product will show, as previouslydescribed, a pattern of coarsely and more finely creped areas, whichdifferentially creped areas have been found to be responsible for theunique combination of improved structural stability, with low densityand high bulk characteristics of the product.

As previously described, at least about 15 percent and not more thanabout percent of the total area of the finished web should be coarselycreped, with the remainder of the area more finely creped. If more thanabout 85 percent of the total area of the web is coarsely creped, thestructural stability of the web is impaired. In addition, the web willflatten out under compressive force and the initially increased bulkwill be lost. If less than about 15 percent of they total surface of theWeb is coarsely creped, the tissue product does not have the low densityand high bulk to the degree desired by the present invention. Aspreviously indicated, the preferred range for the coarsely creped areasis between about 40 percent and about 60 percent.

As previously described, the release agent of the pres ent invention maybe one or more compatible compounds miscible with water or othervolatile solvents and having an oiliness value or coefficient offriction of less than 0.3 at 20 C.

As used in this specification, the degree of oiliness expressed as thecoefiicient of friction is based on data obtained with the modifiedDeeley machine as used for static friction measurements in thecommercial testing of lubricants. This machine consists of two opposinghard steel surfaces, one, a disc about 4 inches in diameter, and theother, three /2 inch diameter balls equally spaced around a circle 3inches in diameter on the underside of a circular carriage. The carriageengages with a torque measuring device consisting of a coiled springwith an indicating mechanism. The pressure between the surfaces can bevaried by loading the carriage with weights. The disc or lower frictionsurface is carried in a bath which contains the lubricant under test,and a gas ring is provided under the bath for heating the lubricant, thetemperature being measured by a thermocouple in the bath.

The machine is operated by slowly rotating the disc by means of anelectric motor and gearing. The frictional resistance between thesurfaces causes rotation of the carriage against the action of thespring, and thedisc is rotated until slipping of the surfaces occurs,when a pawl-and-ratchet mechanism prevents the spring from unwinding.The torque produced by the spring on the carriage at slip is thus equalto the friction torque and, as the total load is known, the coefficientof friction is easily obtained. This value is a measure of the boundarylubrication afforded by the substance tested.

The Deeley machine, the scale of oiliness values and the associated testare described in detail in the Journal of the Institute of Petroleum,vol. 26, No. 195, January 1940, pages 1 to 18, A. Fogg and S. A.Hunwicks, The Static Friction of Lubricated Surfaces. Wherever referenceis made to degree of oiliness or coefficient of friction in thespecification and claims, it falls under the above description.

It has been found that at 20 C. the oiliness value or coefiicient offriction for steel on steel is 0.6. With benzene present, the value is0.5, with alcohol 0.42, with trichlorethylene 0.33, and with glycerol0.2, Mineral oils and fatty oils have values in the range from about0.12 to 0.15, while oleic acid has an exceptionally low value of about0.06.

Examples of release agents which are suitable for the purposes of thepresent invention are the following:

Soaps comprising the sodium salts of oleic, stearic, and other fattyacids; emulsified mineral oil; wax emulsions; silicone emulsions;diglycol laurate; polyethylene glycol di-laurate; emulsified fatty acidsof 6 to 18 carbon atom chain length, such as oleic, ricinoleic,palmitic, stearic and lauric acids; triethylene glycol; sulfonatedcastor oil; rewetting agents of the fatty ester type, and alkyl arylpolyether alcohols; alkyl ketene dimers, such as the ketene dimer of afatty acid of 12 to 18 carbon atom chain length; softening agents of thesulfonated long chain hydrocarbon type; and, quaternary ammoniumchlorides, such as dihydrogenated tallow di-methyl ammonium chloride.

The amount of release agent necessary to effect the differentialreleasing will depend on the oiliness of the release agent, the type oftissue web being released, the temperature of the drier cylinder surfaceand other factors. As previously indicated, the release agent should beutilized in a sufficient amount to efiect the desired differentialcreping but preferably should not be more than that which can beabsorbed by the web on the drier. That is, retention of excess releaseagent on the drier after differentially creping off the web isundesirable. The amount of an agent may vary as much as 0.5 to 50 poundsper ton of tissue web, depending on the type of furnish and basis weightof the web utilized, the type and amount of differential crepingdesired, and the type of releaseagent used.

The selection of the particular release agent may depend not only on itsoiliness value but also on other characteristics of or imparted byparticular release agents: water repellency, absorbency, softness,color, toxicity, odor, bactericidal and antimycotic properties,

and the like.

Since only a relatively minute amount of the release agent need beutilized in practicing the present invention, the cost of achieving thedifferential creping effect is generally slight. Moreover, the greatincrease in bulk (up to 100 percent) over webs creped in theconventional manner results in a considerable lowering of the total costof products assembled from differentially creped webs over comparableproducts made from conventionally creped webs.

In accordance with the method of the present invention, a plurality ofthe differentially dry creped expanded cellulosic tissue webs or sheets,fabricated as previously described, are then assembled in superposedrelation to provide the desired multi-ply, cellulosic tissue product.For many purposes, the individual plies of the product adheresufficiently together so that no other uniting means are required.However, when the product is to be subjected to considerable handling,it may be desirable to unite the plies to a greater extent by embossingor other suitable means.

The following examples set forth certain features of the presentinvention:

Example I An unbleached cellulosic furnish, comprising primarilyreclaimed fibers obtained from kraft cuttings and corrugates, wasprocessed in a conventional manner on a commercial tissue making machineto produce a cellulosic tissue web having a basis weight of 5.34 poundsper ream of 3,000 square feet, on a bone dry basis, before creping.While the web was being dried to about percent by weight moisturecontent in less than one second on a 12-foot diameter Yankee drieroperating at about 190 F. surface temperature and a surface speed ofapproximately 1,600 feet per minute, a 0.167 percent,

by weight, oil-in-water emulsion of a release agent, in

a 8 this case, the ketene dimer of a fatty acid of 18 carbon atom chainlength, was jetted onto the surface of the Yankee drier cylinder at 40pounds per square inch pressure through a microjet spray boom. Themicrojet spray boom had nozzles of 0.008 inch diameter spaced at 4 inchintervals across the entire width of the 12 feet diameter cylinder. Theketene dimer was utilized in an amount of about 1.23 pounds per ton oftissue product.- The boom was located about .5 inch from the exposedsurface of the drying cylinder, between the crep ing doctor blade andthe associated press roll, about 24 inches from the pressure roll nip.The boom was so positioned as to allow time for the water to evaporatefrom the release agent before the sprayed-on material reached the pressroll, thereby preventing the release agent from spreading in thepressure nip between the press roll and drier surface. The web wascreped off the drier with a standard creping doctor blade at a creperatio of 2.00. The diiferentially creped web had roughly parallel linesof coarse crepe and fine crepe, each line of creping being about /3 inchwide. The coarsely creped areas and the finely creped areas eachaccounted for about 50 percent of the total area of the web. The finelycreped areas had about 32 crepes per inch. The coarsely creped areas hadabout 15 crepes per inch.

A plurality of plies of the differentially dry creped web were assembledin random superposed relation into a finished tissue product. Thisproduct and a control product, dry creped to the same crepe ratiowithout the use of a pattern of release agent on the drier, weremeasured for height after 10 days aging. It was found that thedifferentially creped product had an average of 43.5 percent greaterbulk than the conventionally creped control product. The density of theproduct of the present invention was 1.95 pounds per cubic foot ascompared with 2.9 pounds per cubic foot for the control. The product wassuitable for a variety of uses, including a packing material, paddingand wiping cloth.

It is normal practice in the industry to permit creped wadding productsto age before taking bulk and density measurements, in order to allow itto establish a moisture equilibrium with its environment and avoidunnecessary variability caused by shrinkage.

Bulk measurements were made using the conditions set forth in paragraph4.5 of Federal Specification PPP- C-843 Cushioning Material, Cellulosic.Density was computed as outlined in paragraph 4.8 of the same FederalSpecification.

Example 11 A furnish comprised essentially of bleached sulfate fiber wasprocessed in the manner described in Example I to obtain a tissue web.The formed cellulosic tissue web had a drier basis weight before crepingof 4.60 pounds per ream of 3,000 square feet. A 0.167 percent, byweight, oil-in-water emulsion of the ketene dimer of a fatty acid of 18carbon atom chain length was microjetted at 60 pounds pressure, onto thesurface of the Yankee drier of Example I operating at approximately1,600 feet per minute surface speed, and, utilizing the same equipmentand the same point of application as set forth in Example I. The ketenedimer was utilized in an amount of about 1.37 pounds per ton of tissueprod net. The web was dry creped off the drier with a standard crepingdoctor blade at a crepe ratio of 1.94. The differentially creped web hadroughly parallel, /8 inch wide strips of coarse creping and finecreping, each type of creping covering about 50 percent of the totalarea of the web. The finely creped strips had an average of 40 crepesper inch, and the coarsely creped strips 15 crepes per inch.

7 A control sample was fabricated without the use of a pattern ofrelease agent on the drier. A plurality of plies of the differentiallydry creped web were assembled in random superposed relation into afinished tissue product, as were the same number of plies of theconventionally dry creped control tissue web. After days aging of eachof the products, it was found that the difierentially creped product hadan average of 73.2 percent greater bulk than the conventionally crepedcontrol product. The density of the product of the present invention was2.0 pounds per cubic foot while that of the conventional product was 3.3pounds per cubic foot. The product of the present invention was suitablefor use as a wiping agent, padding means and packing material, amongother uses.

Example 111 A furnish comprised essentially of bleached sulfate fiberwas processed into a cellulosic tissue web in the same manner as setforth in Example I. The web had a drier basis weight before creping of4.80 pounds per ream of 3,000 square feet. A water solution containing0.33 percent by weight of diglycol laurate was then microjetted at 120pounds pressure onto the surface of the Yankee drier of Example Ioperating at a surface speed of approximately 1,600 feet per minute. Themicrojetting equipment was the same as was utilized in Example I, as wasthe point of application of the release agent. The diglycol laurate wasutilized in an amount of about 6.3 pounds per ton of tissue product. Theweb was differentially dry creped off the drier at a crepe ratio of1.94. The resulting differentially dry creped web had an appearancecomparable to the webs of Examples I and II, that is, approximately 50percent of the web was coarsely creped and approximately 50 percent wasfinely creped.

The finely creped areas had about 37 crepes per inch and the coarselycreped areas about 14 crepes per inch.

A control dry creped tissue web was fabricated without using a patternof diglycol laurate or other release agent on the drier. The webs wereplied-up to form the differentially dry creped tissue product of thepresent invention and the conventionally dry creped control tissueproduct. After 10 days of aging, the two products were compared and itwa found that the tissue product of the present invention had an averageof 48.6 percent greater bulk than the control tissue product. Thedensity of the product of the present invention was 2.0 pounds per cubicfoot, while that of the conventional product was 3.3 pounds per cubicfoot. The product of the present invention was particularly suitable foruse as a packing material, as well as a wiping agent and padding means.

Example IV An unbleached cellulosic furnish comprising primarilyreclaimed fibers obtained from kraft cuttings and corrugates wasprocessed in the manner described in Example I to obtain a tissue web.The formed cellulosic tissue web had a drier basis weight before crepingof 5.34 pounds per ream of 3,000 square feet. A .167 percent by weightoil-in-water emulsion of fatty acid of 18 carbon atom chain length wasmicrojetted at 20 pounds pressure onto the surface of the Yankee drierof Example I operating at approximately 1,800 feet per minute surfacespeed, and utilizing the same equipment and the same point ofapplication as set forth in Example I. The fatty acid was used in theamount of about 1 pound per ton of product. The Web was dry creped offthe drier with a standard creping doctor blade at a crepe ratio of 2.00.The differentially creped web had roughly parallel, inch wide strips ofcoarse creping and fine creping, each type of creping covering about 50percent of the total area of the web. The finely creped strips had anaverage of 40 crepes per inch and the coarsely creped strips aboutcrepes per inch.

A dry creped control sample was made without using a pattern of fattyacid or other release agent on the drier. The webs were plied up to formthe differentially dry creped tissue product of the present inventionand the control conventionally dry creped tissue product. After 10 daysof aging, the two products were compared and tion had an average of 95percent greater bulk than the control tissue product. The density of theproduct was 1.58 pounds per cubic foot while that of the conventionalproduct was 2.9 pounds per cubic foot. The product of the presentinvention was particularly suitable for use as a packing material aswell as a wiping agent and padding means.

Examples I, II, III, and IV clearly demonstrate the improved resultsobtained by difierentially dry creping cellulosic tissue webs throughthe application of a release agent in a pattern to the drier surface,rather than conventionally dry creping the tissue web to the same creperatio without the use of a pattern of release agent applied to the driersurface. In this connection, the differentially dry creped tissueproducts of the present invention exhibited had 43.5 percent, 73.2percent, 48.6 percent, and 95 percent greater bulk than the respectiveconventionally creped controls. The densities of the multiply tissueproducts made by assembling sheets of the differentially dry creped websmade in accordance with the present invention were correspondingly lowerthan those of the respective conventional control products. Thecommercial importance in reducing the weight and hence the cost oftissue required for a given use or end result will be apparent.

Energy absorption tests were also run on the differentially dry crepedtissue products of the present invention and it was found that theseproducts had up to 50 percent more energy absorption per pound ofproduct under low stress conditions than conventionally creped controlsand up to 40 percent more energy absorption under high stressconditions. Moreover, the tissue products of the present invention werefound to be stable under stress, that is, they did not lose any more oftheir greater bulk after repeated impacts than did an equivalentthickness of conventional lower bulk material. Accordingly, the greaterbulk of these products represents a substantial and permanentimprovement in their cushioning properties.

The differentially dry creped tissue products of the present inventioncan be provided with certain other valuable properties by combining theplies thereof with various other materials which do not substantiallyimpair the improved characteristics of the products. For example,bonding materials may be added during the assem'bling of the plies ofthe product of the present invention into a finished unitaryconstruction.

The number of plies of the tissue products of the present invention arevaried so as to provide the bulk and cushioning properties required forany given use.

As is seen from the above, the differentially creped tissue products ofthe present invention constitute an important novel product havingcertain highly advantageous characteristics not present in the drycreped tissue products previously known in the art. Moreover, theproducts of the invention can be manufactured at high speed and in aneconomical manner on existing papermaking equipment. These products havethe necessary low density, high bulk and surface characteristics for useas packing materials, wiping cloths, padding agents and the like and, asabove noted, when used for these purposes, have important advantagesover the prior art products.

Other suitable modifications of the dilferentially dry creped cellulosictissue products of the present invention and the method of making thesame, as are within the skill of those versed in the art, arecontemplated as being within the scope of the present invention.

What we claim is the following:

1. A method of fabricating an improved dry creped cellulosic tissueproduct, said method including the steps of water-laying a web ofcellulosic tissue, drying the formed tissue web on a heated rotatingmember to a moisture content of between about 3 and about 14 percent byweight, applying to the surface of said rotating member before saidsurface contacts said web a nonit was found that the tissue product ofthe present invenmigrating pattern of fluid release agent having anoiliness value of less than 0.3 at 20 C. as measured on the modifiedDeeley machine, said pattern of release agent being applied tosaid'rotating member in an amount suflicient to decrease to apredetermined extent the tendency of between about 15 percent and about85 percent of said web to adhere to said rotating member and not morethan an amount completely absorbable by said web on said member,diiferentially creping the dried Web from said member to a crepe ratiofor said web of between about 1.25 and about 2.5, and assembling pliesof said differentially creped web in superposed relation to form afinished cellulosic tissue product.

2. A method of fabricating an improved dry creped cellulosic tissueproduct, said method including the steps of water-laying a web ofcellulosic tissue, said web having a basis weight between about 3.5 andabout 15 pounds per ream of 3,000 square feet, on a bone dry basis,drying the formed tissue web on a rotating drying member to a moisturecontent of between about 3 and about 14 percent by weight, applying tothe surface of said rotating member before said surface contacts saidweb a nonmigrating pattern of a release agent having an oiliness valueof less than 0.3 at 20 C. as measured on the modified Deeley machine,said pattern of release agent being applied to the surface of saidrotating member in an amount sufiicient to decrease to a predeterminedextent "the tendency of between about 15 percent and about 85 percent ofsaid web to adhere to said rotating member and notmore than an amountcompletely absorbable by said web on said rotating member,differentially creping the dried web from said rotating member at acrepe ratio between about 1.25 and about 2.5 to form a differentiallydry creped tissue web having alternating coarsely creped and finelycreped areas, said coarsely creped areas comprising about 15 percent andabout 85 percent of the total area of said web, said coarsely crepedareas having between about 5 crepes per inch and about 30 crepes perinch, the remaining area of said web comprising finely creped areashaving between about 20 crepes per inch and about 200 crepcs per inch,and assembling a plurality of plies of said differentially creped tissueweb in superimposed relation into a finished cellulosic tissue producthaving a density between about 1.5 and about 2.0 pounds per cubic foot.

3. A method of fabricating an improved dry creped cellulosic tissueproduct, said method including the steps of water-laying a web ofcellulosic tissue, said web having a basis weight before creping ofbetween about 4 and about pounds per ream of 3,000 square feet, on abone dry basis, drying the formed tissue web on a heated rotating drumto a moisture content between about 3 and about 14 percent by weight,applying to the surface of said drum before said surface contacts saidweb a nonmigrating pattern of release agent having an oiliness value ofless than 0.3 at 20 C. as measured on the modified Deeley machine, saidpattern of release agent being applied to the surface of said drum in anamount sufficient to decrease to a predetermined extent the tendency ofbetween about 40 percent and about 60 percent of said web to adhere tosaid drum and not more than an amount completely absorbable by said webon said drum, differentially creping the dried web from said drum at acrepe ratio ,of about 2.0 to form a differentially dry creped tissue webhaving alternating coarsely creped and finely creped areas, saidcoarsely creped areas comprising between about 40 percent and about 60percent of the total area of said Web and having between about 10 andabout 20 crepes per inch, the remaining area of said web comprisingfinely creped areas having between about 30 and about 50 crepes perinch, and assembling a plurality of plies of said differentially crepedtissue web in superposed relation to form an improved cellulosic tissueproduct having a density between about 1.5 and about 2.0 pounds percubic foot.

4. A method of fabricating an improved dry creped 'cellulosic tissueproduct, said method including the steps of water-laying a web of tissuefrom a furnish comprising percent wood pulp, said web having a basisweight before creping of between about 4 and about 10 pounds per ream of3,000 square feet, drying the formed tissue web on a heated rotatingdrum to a moisture content of between about 3 and 14 percent by weight,continuously applying to the surface of said drum before said surfacecontacts said Web a non-migrating pattern of an aqueous solution ofemulsion of a release agent having an oiliness value at 20 C. of lessthan 0.3 as measured on the modified Deeley machine, and selected fromthe group including diglycol laurate, fatty acids of 6 to 18 carbon atomchain length, alkyl ketene dimers, and mineral oil, said pattern beingapplied in an amount of between 1 and 10 pounds per ton of tissueproduct, that is, an amount sufiicient to decrease the tendency ofbetween about 40 percent and about 60 percent of said web to adhere tosaid drum and not more than an amount completely absorbableby said webon said drum, differentially dry creping said dried web from said drumat a crepe ratio of about 2.0 to form a differentially dry creped tissueweb having alternating coarsely creped and finely creped areas, saidcoarsely creped areas comprising between about 40 percent and about 60percent of the total area of said web and having between about 10 andabout 20 crepes per inch, the remaining area of said web comprisingfinely creped areas having between about 30 and about 50 crepes perinch,and assembling a plurality of plies of said difiFerentially dry crepedtissue Web in superposed relation to form an improved cellulosic tissueproduct having a density of between about 1.3 and about 2.0 pounds percubic foot.

References Cited in the file of this patent UNITED STATES PATENTS Re.23,637 Montgomery Mar. 24, 1953 1,534,622 Wandel Apr. 21, 1925 2,077,438Rowe Apr. 20, 1937 2,132,016 Du Bois Oct. 4, 1938 2,725,640 VoigtmanDec. 6, 1955 OTHER REFERENCES Casey: Pulp and Paper, vol. II, 1952,Interscicnce Publishers, Inc., NY, page 844.

1. A METHOD OF FABRICATING AN IMPROVED DRY CREPED CELLULOSIC TISSUEPRODUCT, SAID METHOD INCLUDING THE STEPS OF WATER-LAYING A WEB OFCELLULOSIC TISSUE, DRYING THE FORMED TISSUE WEB ON A HEATED ROTATINGMEMBER TO A MOISTURE CONTENT OF BETWEEN ABOUT 3 AND ABOUT 14 PERCENT BYWEIGHT, APPLYING TO THE SURFACE OF SAID ROTATING MEMBER BEFORE SAIDSURFACE CONTACTS SAID WEB A NONMIGRATING PATTERN OF FLUID RELEASE AGENTHAVING AN OILINESS VALUE OF LESS THAN 0.3 AT 20*C. AS MEASURED ON THEMODIFIED DEELEY MACHINE, SAID PATTERN OF RELEASE AGENT BEING APPLIED TOSAID ROTATING MEMBER IN AN AMOUNT SUFFICIENT TO DECREASE TO APREDETERMINED EXTENT THE TENDENCY OF BETWEEN ABOUT 15 PERCENT AND ABOUT85 PERCENT OF SAID WEB TO ADHERE TO SAID ROTATING MEMBER AND NOT MORETHAN AN AMOUNT COMPLETELY ABSORBABLE BY SAID WEN ON SAID MEMBER,DIFFERENTIALLY CREPING THE DRIED WEB FROM SAID MEMBER TO A CREPE RATIOFOR SAID WEB OF BETWEEN ABOUT 1.25 AND ABOUT 2.5, AND ASSEMBLING PLIESOF SAID DIFFERENTIALLY CREPED WEB IN SUPERPOSED RELATION TO FORM AFINISHED CELLULOSIC TISSUE PRODUCT.